The present invention relates generally to nozzle heads. More particularly, it relates to a nozzle head with a plurality of nozzles, a nozzle carrier rotatable about an axis and driveable by a reaction of pressurized water discharged from the nozzles, a brake for braking a rotary movement of the nozzle carrier, a stationary housing provided with a pressurized water connection, and a hollow shaft extending from the pressurized water connection and having a central passage which accommodates a sleeve, as well as a labyrinth gap seal provided between the sleeve and a limiting wall of the central passage.
Nozzle heads of the above mentioned general type are known in the art. One of such nozzle heads is disclosed for example in the U.S. patent application Ser. No. 07/390,187.
Such a nozzle head utilizes the principle of reaction driven rotatable tools and includes a reaction impeller. Their rotary speed is limited by hydraulic, mechanical or other eddy current brakes. The jets which discharge from the rotatable nozzles form circular striking lines on the object to be treated. They are compressed at the right side and the left side of the displacement direction of the tool very intensely and thereby a substantially strong degradation power is produced. Due to the displacement of the tool, strongly degraded regions are produced left and right of the straight tangents in the displacement direction.